Progress of time and increasing quality of people's life have spawned diversified designs of household articles used by people to meet various requirements. Take chairs for instance, there are many types of chairs made of metal to get the benefits of stronger strength and greater durability. To make such chairs producers generally have to prepare multiple types of components, such as front legs, rear legs, a seat cushion, a backrest and the like that are formed by stamping metal tubes or plates, then assemble these components by welding or riveting. As a result, chairs made of metal usually take more manpower and cost higher than the chairs made of other material.
For instance, Taiwan patent No. 277284 discloses an improved assembly structure for a chair leg bracket. The leg bracket includes a plurality of support bars, a plurality of bridging bars welded between the plurality of support bars and a plurality of transverse bars welded on the plurality of bridging bars. Hence it can be assembled easily by welding. However, for mass production of the leg bracket at factories, the support bars, the bridging bars and the transverse bars must be first welded in one piece, then surface treatment has to be made, and finally the backrest and seat cushion are assembled. As the leg bracket finished by welding is bulky, it takes a lot of storage space and creates a great deal of troubles in the assembly plant. Moreover, because the leg bracket cannot be disassembled, transportation or packing into containers also is more cumbersome and results in higher transportation cost.
In addition, in the conventional techniques, if a chair is assembled and fastened by nuts and bolts, the nuts often need to be welded inside a chair tube. Such a welding process also increases the cost. All this indicates that how to design a chair that can be easily assembled without welding is an issue yet to be resolved.